The preparation conditions of 1,1-difluoroethene-Ar clusters has been investigated by photoionization using synchrotron radiation. The nature of the products has been identified by a quadrupole mass ... [more ▼]

The preparation conditions of 1,1-difluoroethene-Ar clusters has been investigated by photoionization using synchrotron radiation. The nature of the products has been identified by a quadrupole mass spectrometer. [less ▲]

The unimolécular reactions of the fluoromethane ion have been investigated by the threshold photoelectron photoion coincidence technique (TPIPECO). The breakdown curves have been measured in the energy ... [more ▼]

The unimolécular reactions of the fluoromethane ion have been investigated by the threshold photoelectron photoion coincidence technique (TPIPECO). The breakdown curves have been measured in the energy range between the adiabatic ionization potential of 12.53 eV and 21 eV. In this enery range the formation of the CH2F+, CHF+, CH2+, CH3+, and CF+ fragment ions is observed. The appearance energies (AE) for these ions at 300K are 13.2, 13.91, 13.93, 14.51 and <17.7 eV respectively. The 0K threshold energy for the formation of CH2F+ ions is 13.37 eV. Two different pathways for the unimolecular reaction of the fluoromethane ion can be distinguished.The reaction proceeding through the electronic ground state of the ion is entirely statistical. In contrast to this the reaction occurring through the first electronic excited state shows non-statistical behaviour. The two pathways are distinguished via the kinetic energy released in the respective dissociation channels. While all thermodynamically allowed reaction channels are observed on the ion ground state potential, the first excited state seems to decay predominantly by F loss reaction. [less ▲]

Using synchrotron radiation, we have investigated the threshold photoelectron spectrum of NH3 between 10-30 eV photon energy. In contrast to the He(I)-photoelectron spectrum, the threshold photoelectron ... [more ▼]

Using synchrotron radiation, we have investigated the threshold photoelectron spectrum of NH3 between 10-30 eV photon energy. In contrast to the He(I)-photoelectron spectrum, the threshold photoelectron spectrum shows three bands between 10 and 21 eV. The first band is dominated by the vibrational autoionization of the 5a1, the 6a1 and the 6pe Rydberg series. Between the first and second bands a new contribution, starting at 13.26 eV, is assigned to the autoionization of (a) member(s) of Rydberg series converging to the e-1 ionization continuum. Its (their) autoionization populates the upper vibrational levels of the NH3+ (X2A1) state. From about 14.5 eV the A2E band structures are identified. However, differences between the A2E band shapes in the He(I)- and the threshold photoelectron spectra suggest that very likely autoionization contributions are involved in the latter spectrum. These phenomena could play a role in the production of the NH2+ and NH+ fragment ions. The last very weak band, at about 25 eV in the photoelectron spectrum is assigned to the NH3+(B2A1) state. [less ▲]

An ion retarding potential difference (IRPD) method has been used to investigate the ion yield and the kinetic energy distributions of N+/N2 produced by photoionization mass spectrometry using synchrotron ... [more ▼]

An ion retarding potential difference (IRPD) method has been used to investigate the ion yield and the kinetic energy distributions of N+/N2 produced by photoionization mass spectrometry using synchrotron radiation. Photoion yield curves of energy selected N+ ions are deduced. Translational energy distributions of N+ at the energies of the N(1s)->pi*, N(1s)->(nl)1 and above the N(1s)-1 threshold are determined. Comparison is made with previous photoion-photoelectron coincidence work using time-of-flight (TOF) measurements. [less ▲]

Core level excitation of weakly bonded atomic and molecular species is reported. Excitations into unoccupied orbitals with valence and Rydberg character as well as into the corresponding K- and L-continua ... [more ▼]

Core level excitation of weakly bonded atomic and molecular species is reported. Excitations into unoccupied orbitals with valence and Rydberg character as well as into the corresponding K- and L-continua are compared with the isolated and condensed species. Core level excitation of clusters is also accompagned with extensive fragmentation of singly and doubly charged clusters. Coincidence techniques such as photoelectron-photoion-coincidences (PEPICO) and photoion-photoion-coincidence (PIPICO) are used to study the photochemical fragmentation pathways of core excited clusters. Kinetic energy releases related to charge separation of cluster dications (Coulomb explosion) are derived from PIPICO spectra. The fragmentation energetics is discussed in relation to cluster dication threshold energies. [less ▲]

The threshold- and CIS-photoelectron spectrum of SO2 has been measured using synchrotron radiation. It is compared to the He(I)-photoelectron spectrum measured with the same instrument under the same ... [more ▼]

The threshold- and CIS-photoelectron spectrum of SO2 has been measured using synchrotron radiation. It is compared to the He(I)-photoelectron spectrum measured with the same instrument under the same conditions. Several additional vibrational fine structures are observed between the first and the second bands. These are interpreted in terms of autoionization also detected in the CIS-spectra. At higher photon energies, band maxima are measured at 19.2 eV, 20.6 eV and 23.5 eV. [less ▲]

The IRPD method is applied to the dissociative ionization in the inner-shell ionization region for NO+, N2+, O+, N+ and N++/N2O. Particular attention has been focussed on the production and ion kientic ... [more ▼]

The IRPD method is applied to the dissociative ionization in the inner-shell ionization region for NO+, N2+, O+, N+ and N++/N2O. Particular attention has been focussed on the production and ion kientic energy distribution of H+/NH3. [less ▲]

The photoionization of NH3 and its isotopomers is measured between 10-12 eV photon energy by using synchrotron radiation. The abundant autoionization structure observed in the ionization efficiency curves ... [more ▼]

The photoionization of NH3 and its isotopomers is measured between 10-12 eV photon energy by using synchrotron radiation. The abundant autoionization structure observed in the ionization efficiency curves is analyzed. [less ▲]

A new method is described to obtain photoionization efficiency curves of kinetic energy-selected fragment ions. The method is tested and discussed in the case of the dissociative photoionization yields of ... [more ▼]

A new method is described to obtain photoionization efficiency curves of kinetic energy-selected fragment ions. The method is tested and discussed in the case of the dissociative photoionization yields of NO+ and O+ from N2O. The attention is focussed on the dissociative autoionization processes in the threshold region, in the Franck-Condon region of the N2O(A2Sigma+) state and in the Franck-Condon gap between the A2Sigma+ and B2Pi states. [less ▲]

The photoionization efficiency curves of the four isotopomers of NH3 have been recorded using synchrotron radiation. The abundant fine structure has been interpreted in terms of vibrational structure of ... [more ▼]

The photoionization efficiency curves of the four isotopomers of NH3 have been recorded using synchrotron radiation. The abundant fine structure has been interpreted in terms of vibrational structure of Ryberg series which autoionize. [less ▲]

The photoionzation efficiency curves of NH3 and its three isotopomers have been investigated in the photon energy range of the first ionized state. From the analysis of the corresponding vibrational ... [more ▼]

The photoionzation efficiency curves of NH3 and its three isotopomers have been investigated in the photon energy range of the first ionized state. From the analysis of the corresponding vibrational structure, wavenumbers and anharmonicity constants are deduced. The detailed investigation of the abundant autoionization structure tends to show the adiabatic ionization energy to be 10.072+/-0.010 eV for NH3, NH2D and NHD2 and 10.083+/-0.010 eV for ND3. All autoionization features were classified in vibrational progressions (nu2 bending mode) belonging to nasa1 (or nd) and npe (n=5, 6, 7) Rydberg series. Vibrational autoionization occurs through Delta v transitions up to -9. A qualitative analysis of the intensity distribution of these series strongly supports that transitions involving odd Delta v values are favoured. This observation can be understood by applying group theoretical considerations to the theory of vibrational autoionization. [less ▲]

The vacuum ultraviolet absorption spectra of the three fluorochloroethene isomers were measured in the 6-13 eV photon energy range. Additionally, the HeI and NeI photoelectron spectra were recorded. The ... [more ▼]

The vacuum ultraviolet absorption spectra of the three fluorochloroethene isomers were measured in the 6-13 eV photon energy range. Additionally, the HeI and NeI photoelectron spectra were recorded. The assignment of the various photoelectron bands is based on MNDO calculations. The vaccum UV absorption spectral features were classified in terms of Rydberg series converging to the first and second ionization energy. Besides the typical pi-pi* transition, other valence transitions were observed and tentatively assigned. In the geminal isomer spectrum the dominant Rydberg series converge to the first ionization limit at 10.02 eV, in the cis and trans isomers the most intense Rydberg transitions converge to the second ionization energy at 11.87 and 12.03 eV respectively. The first ionization energies of these latter compounds, obtained by Rydberg series analysis, are 9.89 and 9.87 eV respectively. An assignment of the vibrational structure observed in both spectra is proposed. [less ▲]

Dissociative photoionization of O2 has been investigated by using the ion retarding potential for the translational energy analysis of the O+ fragment. Synchrotron radiation is used as a light source ... [more ▼]

Dissociative photoionization of O2 has been investigated by using the ion retarding potential for the translational energy analysis of the O+ fragment. Synchrotron radiation is used as a light source. Ionization efficiency curves have been recorded at several retarding potential settings. [less ▲]